Electronic coin testing apparatus

ABSTRACT

An electronic coin testing apparatus for comparing a coin travelling down a chute with a standard coin, of the type including means for producing a difference signal depending on the difference between the effect produced by the coin to be tested and that produced by the standard coin, the said difference signal decreasing from a predetermined value to zero and rising again as a coin identical with the standard coin passes a given position in the chute comprises a threshold device producing or not producing a predetermined threshold output signal depending on whether or not the difference signal exceeds a given value, a gate for separating accepted coins from rejected coins, and discriminating means for actuating the gate arranged to accept a coin only if there is a threshold output signal and it is not followed by a second such signal within a predetermined period of time.

I United States Patent 11 1 1111 3,741,363 Hinterstocker June 26, 197 3ELECTRONIC COIN TESTING APPARATUS Primary Examiner-Robert B. Reeves [76]Inventor figg near Assistant Examiner-David A. Scherbel Holz c en,Germany Attorney-Spencer & Kaye [22] Filed. June 15, 1971 ABSTRACT [21]Appl' 153228 An electronic coin testingapparatus for comparing a cointravelling down a chute with a standard coin, of [30] ForeignApplication Priority Data the type including means for producing adifference J 16, 1970 Gen-any n p 20 29 751.2 signal depending onthedifference between the effect produced by the coin to be tested andthat produced by 52 US. Cl. 194 100 A, 209/1111; the standard win, thesaid difference signal decreasing [51] Int. Cl. G07! 3/02 from apredetermined Value to Zero and rising again as 581 Field of Search194/100 R, 100 A; a coin identical with the standard will passes a given73 1 3; 209 1113 position in the chute comprises a threshold deviceproducing or not producing a predetermined threshold 5 References i doutput signal depending on whether or not the differ- UNITED STATESPATENTS ence signal exceeds a given value, a gate for separatingaccepted coins from rejected coins, and discriminating gag 35 agi 6 3:means for actuating the gate arranged to accept a coin 3401780 9/1968Jumeml) 194]00 R only if there is a threshold output signal and it isnot fol- 315991771 8/1971 l-linterstocker 194/100 A 10%! byva such$181131 predetermined period of time.

7 Claims, 9 DrawingFigures PAIENIEDJlm2s 191s SHEET 1 BF 1 N VENT OR.Adolf Hinters'rocker ATTORNEYS memmiuuz ms 3.741; 363

SHEET 2 OF 2 Fig.5

L5 I Time t 1 Time t Time t Time t c i v i: l

I 5 Time t pzumsj Time t 0 g n H I L-Zllms Time t Time i A-\/- 5 7 Timet imviamuii;

Adolf Hinierstocker BY: J

ATTORNEYS.

ELECTRONIC COIN TESTING APPARATUS BACKGROUND OF THE INVENTION Thepresent invention relates to electronic coin testing apparatus forcomparing a coin travelling down a chute with a standard coin. In thistype of testing apparatus a difference signal is produced which dependson the difference between the effect produced by the coin to be testedand that produced by the standard coin. This difference signal decreasesfrom a predetermined initial value down to zero and then returns to itsinitial value as a coin identical with the standard coin passes a givenposition in the chute. A threshold device produces a predeterminedthreshold output signal the difference signal exceeds a given value. Agate separates accepted coins from the rejected coins. The gate isactuated by a discriminating means.-

In one embodiment of the testing apparatus, the chute extends between aprimary coil connected to a source of alternating current and a firstsecondary coil inductively coupled with the primary coil. The secondarycoil is coupled to the gate, beyond the coils in the direction of travelof the coins. A second secondary coil is mounted on the side of theprimary coil remote from the coin chute, and is inductively coupled withit, and is connected in series with the first secondary coil in suchdirection that the voltages induced by the primary coil in the twosecondary coils are subtracted, with a device for holding a standardcoin between the primary coil and the second secondary coil.

Such a coin testing device is described in my earlier patent applicationSer. No. 852,531 filed Aug. 1969, now US. Pat. No. 3,599,771. In thisknown coin testing device the testing must take place during arelatively short space of time, during which the coin to be tested(travelling down the chute) is situated exactly symmetrically with thestandard coin For this purpose provision has been made for a switchingdevice actuated by the coin to be tested, which device switches on thetest circuit at the right moment and compares the coin to be tested,which must not move appreciably during the short testing period.

Such switching devices, which test the coin passing through the coinchute at the moment when the coin is in the testing position between theprimary coil and the secondary coil, give rise to certain problems.Mechanical switching devices, e. g. a rocker which is actuated by thecoin to be tested, and on which a small magnet is mounted for theactuation of a reed contact, are sensitive, liable to interference and,with considerable use, wear relatively quickly. Contact-free switchingdevices, e.g. switching devices with capacitive and inductive sensors,are costly and also sensitive as well as susceptible to interference.

SUMMARY OF THE INVENTION An object of the present invention is toprovide such an electronic coin testing device in which it is notnecessary to provide a coin-controlled switching device which limits thetesting to a predetermined short space of time.

According to the invention discriminating means is provided foractuating the gate, arranged to accept a coin only if there is athreshold output signal and it is not followed by a second such signalwithin a predetermined period.

The discriminating means preferably include a bistable circuit arrangedto be alternately set and reset by successive threshold output signals,to produce a flipflop output signal arranged to actuate the gate througha time constant circuit to accept a coin only if the flipflop outputsignal persists for a predetermined period. The time constant circuitconveniently includes an integrating operational amplifier, and may alsoinclude a level-responsive trigger device.

Resetting means may be provided for resetting the bistable circuit, ifit is not already reset, after a second predetermined period, longerthan the first predetermined period (in readiness for the next coin).Such resetting means may include a delay device connected between theoutput of the time constant circuit and a resetting input to thebistable device.

The invention may be put into practice in various ways but one specificembodiment will be described by way of example with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified cross-sectionalview through the coin chute and the measuring coils of an electroniccoin-testing device, on the line l1 of FIG. 2;

FIG. 2 is a cross-section on the line 2-2 of FIG. 1;

FIG. 3 is a circuit diagram of an electronic cointesting deviceaccording to the invention;

FIG. 4 is a graphic representation of the attenuation caused by variouscoins to be tested;

FIGS. 5 to 9 are diagrammatic graphs, relating respectively to the coinscorrespondingly numbered in FIG. 4, showing the time progress of signalsat various points in the circuit.

DESCRIPTION OF'TI-IE PREFERRED EMBODIMENT The present coin-testingdevice includes, as usual, a coin chute 10 of rectangular cross-sectionwhich starts at a coin input slot 11. The coin chute extends between aprimary coil 12 and a first secondary coil 14 arranged coaxially withthe primary coil. On the side of the primary coil 12 remote from thecoin chute 10 there is a second secondary coil 16, the two secondarycoils being mounted symmetrically with respect to the primary coil 12.Between the primary coil 12 and the second secondary coil 16 there isdisposed a standard coin 18, i.e. a typicalspecimen of the coins to betested.

In the direction of travel of the coins in the coin chute, beyond thecoil arrangement 12, 14, 16, is a gate containing an abutment 20 whichprotrudes into the coin chute, and may be retracted by a magnet coil(FIG. 3). In the retracted state the gate allows the tested coin toenter a channel for accepted coins 22, while, when the magnet coil isnot excited, the abutment 20 protrudes into the coin chute, so that thetested coin strikes against it and enters a reject channel 24.

The primary coil 12 is connected to an alternating current source 26which may, for example, comprise a transistor oscillator, and whichsupplies an output voltage at a frequency in the range of approximately10 to kHz.

The two secondary coils l4, 16 are connected in series in such directionthat the voltages induced in them by the primary coil 12 are subtractedfrom each other, to produce a difference signal which will be zero whenbetweenthe primary coil 12 and the first secondary coil .14 there isacoin which corresponds exactly to the standard coin 1 8 and liessymmetrically with it.;

The differencesignal of the secondary coils 14, I6 is led via anamplifier30 to a demodulator orrectifier. 32 which supplies a differencesignal A which corresponds I to the envelope of the differential voltageproduced by the series connected secondary coils 14, 16. The output drest value M, as represented in the upperdiagram of FIG.5.

When the coin tojb e .tested has an attenuation smaller thantheattenuationofthestandard coin, as is shown signal A of the rectifier 32is supplied to a level respon-p sive trigger circuit 34, for example aSchmitt trigger circuit, which provides a threshold output signal B aslong as the amplitude of the difference a predeterminedthresholdvalue S.

signal A lies below.

As described so far the arrangement is similar to that I described inthe specification referred to above.

The output of the trigger ciruit 34 is connected to a I (FIG. 2). Theoutputsig nal A has therefore a first zero position x,, when thecoin tobe tested is situated switchover input of a bistable or flip-flopcircuit 36, so

that the latter will be alternately set and resetby successive thresholdoutput signals B, and when set )will supply an output signal C. Thisoutputsignal C, which may be termed a flip-flop output signalis led viaa a coin to be tested is located in the centre position 44',

time constant 38, e.g. an integrating operational amplifier with aninput resistorand a feedback capaciton and if required afurther'level-responsive triggercircuit, to an amplifier 40, the outputof whichactuates the magnetic coil 22 of the gate. I a

The time constant circuit 38 is so designed that gate is actuated onlywhen the duration of the flip-flop output signal C of the bistablecircuit 36 exceeds a predetermined value, in practice about 20 ms.

The output 'signalof the amplifier is'furtherr nore led via a delaydevice 42, which may for example have a delay time of 100 ms, to a resetinput R of thebistable Beforean explanation is given of the modusoperandi circuit 36.

of the present coin testing device a shortexamination will be made ofthe conditions present atthetesting sta;

tion (FIG. 1). I

In coin testing devicesiof the present type the attenu ation ofthecoupling between the primary coill2and Inth'ecircuit ofFIGQ3 thetrigger circuit 34 supplies U .athreshold output signal B as long as theamplitudeof theidifilerence signal A lieskbelow the threshold value S(cf. the upper diagram ofFlGS. 5 to 9). By .t hefon the secondary coil14 by a coin 44 to be tested, located between these coils,is comparedwith the attenuation which the standardjcoin l8causes between theprimarycoil and the second secondary coil 16. Accepted as genuine are suchcoins as have an attenuation which falls within a predetermined range,which in FIG.:4 is

delimited by the horizontal dashed lines. The attenuation of thestandard coincorresponds to the value V at the center of this range.

If a coin, with respect to its attenuation qualitiescor responds exactlyto'the standard coin 18, travels down the 'coin chute 10 between thecoils 12 and 14, the threshold output signal A of the rectifier 32 (FIG.3) alters as a function of time as represented in FIG..5. As long as thecoin has not yet entered the field of influence of the coils, the signalA has a definite rest value M. When the coin begins to enter the spacebetween the coils 12 and 14, the amplitude of the signal A decreasesuntil it finally becomes zero, when the coin'is situated exactly betweenthe coils 12 and 14,,as is shown in FIG. 2 by the continuous circle 44.At this moment, in the known coin-testing devices, the testing of thecoin for genuineness took place, i.e. at this moment the attenuations ofthe coin to be tested and the standard coin were compared. If the cointhen travels further, the amplitude of the signal A rises again to themcoins, w

at 6 in ElGJlpthe output, signal A develops according to the firstdiagram in FIG. If the attenuation is still y 1: smaller and liesoutside thetolerance range, as is shown Cur v eAin FIG. 7. as a a d Ifthevattenuation is slightly greater than thatof the at 7 in FIG. 4, theoutput signal develops according to standard coin, asshown at 8 in FIG.'4, the form of the output'signal as shown in FIG. 8. Theattenua tioneffected bythe cointo be'tested is thenirideed equalf 'to theattenuation of the {standard coin 18 coin to betested finds itself thecentralised position in the: position 44" (FIG. 2 shown doted.When thethe output signalhas a small intermediate maximum,

and'it again becomes zerofata positionx g when the coin to be testedisin a position 44" symmetrical with r t the position 44'- Then, theoutput signal increases again to the rest value. If the coin has anattenuation so great thatit lies outside the tolerance range, as representedyat. 9 in FIG. 4, the development of the output signaI A is asrepresentedin FIG; 9, so that theinterme diate maximum, at afpoint ,xhas a relatively. high value.

Thestate of. affairs depicted above as regards the de velopment of theoutput signal of the rectifier-32 with coins of different attenuation isused in the present in vention todiscriminate between acceptedandrejected thoutthe necessityfor making the test within a definiteinterval of time. 1

coins.

impulse B and thebistable circuit 36is therefore set,

coils 12 and 14, supplies onlya single threshold output and remains setuntil, after for example 120 ms, it is reset by the reset circuit withthe delay device 42, as is represented by the curves C in FIGS. 5, 6 and8.

When, however, the attenuation of the coin to be a tested is as small asis represented at 7 in FIG. 4, the difference signal A (FIG. 7) does notfall below the threshold value S of the trigger circuit 34, the lattercannot supply any threshold output signal, the bistable circuit 36 isnot set and therefore also no impulse can be produced for the actuationof the gate.

, When, on the other hand, the attenuation of the coin to be tested liesabove the upper tolerance limit, as

represented at 9 in FIG. 4, two impulses occur in the threshold outputsignal B as will be easily seen from FIG. 9. The intermediate maximum atx, in this case acbefore the 7 This is possible with "was withattenuation values such as represented at 5, 6, and Sin FIG. 4, asherethe threshold'circuit 34, as the coin passesbetweenthe tuallyexceeds the threshold value S, so that the trigger circuit 34 can for ashort time reset before the difference signal A (FIG. 9) becomes zerofor the second time. The second impulse B, (FIG. 9), however, thenresets the bistable circuit 36 before the time constant member 38 andthe amplifier 40 can respond, and the gate is therefore in this casealso not actuated, so that the tested coin strikes on the abutment 20and is directed into the rejected channel 24.

In the circuit of FIG. 3 the entire testing circuit is thereforecontinuously operative when coins are to be tested. With mains-operatedcoin testing devices the oscillator 26 and the other stages can then beconstantly in operation; with battery-operated coin testing devicesprovision can be made for a quite simple switching device actuated bythe insertion of a coin, which switches on the arrangement for theduration of the test. As these switching processes need not besynchronised with the run of the coin through the testing station, thisswitching arrangement may be made very simple and cheap.

Instead of the. bistable or flip-flop circuit 36 and of the resetcircuit consisting in a delay circuit 42, it is naturally possible touse also other known switching arrangements equivalent in effect.

The values given above for the delay times efiected through the timeconstant circuit 38 and the delay circuit 42 are typical, and haveproved themselves adequately in practice; however, they may be modifiedif desired. The retardation time of the time constant circuit must,however, be at least long enough to make possible resetting of thebistable circuit 36 by the second impulse B (FIG. 9B) to preventactuation of the gate.

The delay circuit 42 must ensure that the abutment 20 of the gateremains retracted from the coin chute until a coin found to beacceptable as a result of the testing is able to enter the channel 22for accepted coins.

The circuits mentioned above and shown in block form in the drawing arepreferably transistoriaed'circuits which may be of known construction.

As various changes could be made in the above disclosed embodimentwithout departing from the scope of invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What I claim is: I

1. In an electronic coin testing apparatus including a signal generatingmeans for producing a test signal in dependence on a coin to be testedin comparison to a standard coin and a control means for producing anacceptance signal only when the maximum value of the test signal fallswithin'preselected boundaries, the improvement wherein the control meanscomprises, in

combination: a rectifier means connected to said signal generating meansfor producing a rectified output of the test signal; threshold valuemeans connected to said rectifier means for producing a threshold outputsignal each time the rectified output of the test signal is within athreshold area defined by the two preselected boundaries; a bistablemeans, receiving a plurality of signals and connected to said thresholdvalue means, for producing a gating signal upon receipt of a firstsignal and turning off the gating signal upon receipt of a secondsignal; a time constant means connected to said bistable means forproducing an acceptance pulse when the duration of the gating signal islonger than a first predetermined time period; and reset means providinga signal for resetting said bistable means after a second predeterminedtime period which is longer than the first predetermined time. period.

2. Apparatus as defined in claim 1 wherein said time constant meansincludes an integrating operational am- 3. Apparatus asdefined in claim2 wherein said time constant circuit further includes a level-responsivetrigger device.

4. Apparatus as defined in claim 1 wherein said reset means includes adelay device connected between the output of said time constant meansand' a resetting input to said bistable means.

5. Apparatus as defined in claim 1 further comprising a chute alongwhich the coin to be tested passes; and wherein said signal generatingmeans includes: a source of alternating current; a primary coilconnected to said current source and arranged on one side of said chute;a first secondary coil inductively coupled with said primary coil andarranged on the side of said chute opposite said primary coil, wherebythe voltage induced in said first secondary coil by the current in saidprimary coil is affected by the coin passing along said chute; a secondsecondary coil inductively coupled with said primary coil and arrangedon the side of said primary coil remote from said chute, whereby thevoltage induced in said second secondary coil by the current in saidprimary coil is affected by a standard coin positioned between saidprimary coil and said second secondary coil; said first and secondsecondary coils being connected in such a manner that the voltagesinduced therein by said primary coil are subtracted.

6. Apparatus as defined in claim 1 wherein the first predetermined timeperiod is selected such that the gat-- ing signal will only be of alonger duration than the first predetermined time period when therectified output of the test signal onlypasses into the threshold areaonce.

7. Apparatus as defined in claim 1 wherein said threshold value meansincludes a Schmitt trigger cir- Clllt.

s s a sn

1. In an electronic coin testing apparatus including a signal generatingmeans for producing a test signal in dependence on a coin to be testedin comparison to a standard coin and a control means for producing anacceptance signal only when the maximum value of the test signal fallswithin preselected boundaries, the improvement wherein the control meanscomprises, in combination: a rectifier means connected to said signalgenerating means for producing a rectified output of the test signal;threshold value means connected to said rectifier means for producing athreshold output signal each time the rectified output of the testsignal is within a threshold area defined by the two preselectedboundaries; a bistable means, receiving a plurality of signals andconnected to said threshold value means, for producing a gating signalupon receipt of a first signal and turning off the gating signal uponreceipt of a second signal; a time constant means connected to saidbistable means for producing an acceptance pulse when the duration ofthe gating signal is longer than a first predetermined time period; andreset means providing a signal for resetting said bistable means after asecond predetermined time period which is longer than the firstpredetermined time period.
 2. Apparatus as defined in claim 1 whereinsaid time constant means includes an integrating operational amplifier.3. Apparatus as defined in claim 2 wherein said time constant circuitfurther includes a level-responsive trigger device.
 4. Apparatus asdefined in claim 1 wherein said reset means includes a delay deviceconnected between the output of said time constant means and a resettinginput to said bistable means.
 5. Apparatus as defined in claim 1 furthercomprising a chute along which the coin to be tested passes; and whereinsaid signal generating means includes: a source of alternating current;a primary coil connected to said current source and arranged on one sideof said chute; a first secondary coil inductively coupled with saidprimary coil and arranged on the side of said chute opposite saidprimary coil, whereby the voltage induced in said first secondary coilby the current in said primary coil is affected by the coin passingalong said chute; a second secondary coil inductively coupled with saidprimary coil and arranged on the side of said primary coil remote fromsaid chute, whereby the voltage induced in said second secondary coIl bythe current in said primary coil is affected by a standard coinpositioned between said primary coil and said second secondary coil;said first and second secondary coils being connected in such a mannerthat the voltages induced therein by said primary coil are subtracted.6. Apparatus as defined in claim 1 wherein the first predetermined timeperiod is selected such that the gating signal will only be of a longerduration than the first predetermined time period when the rectifiedoutput of the test signal only passes into the threshold area once. 7.Apparatus as defined in claim 1 wherein said threshold value meansincludes a Schmitt trigger circuit.